EXCRETION OF BILE. 321 



All procedures, therefore, that induce increased destruction of red blood- 

 corpuscles make the liver rich in hemoglobin and, as a result, cause increased 

 production of bile, also pathologically, as, for example, in the presence of malaria 

 and blood-degenerations. 



Naturally, a normal condition of the liver-cells is necessary for 

 normal secretion. 



For observing the secretion of bile in animals, a biliary fistula is established, 

 the fundus of the gall-bladder being opened somewhat to the right of the xiphoid 

 process, and then being sutured into the abdominal wall, with the aid of a cannula 

 kept constantly open. As a rule, all of the bile will then be discharged externally. 

 If absolute certainty in the latter connection be desired, the common bile-duct 

 should be ligated in two places and divided. Soon after the establishment of a fis- 

 tula, the secretion of bile diminishes. This is dependent upon the removal of 

 the bile from the body. Introduction of bile in the body from some other source 

 again increases the secretion. Various investigators have been able to observe 

 directly biliary fistulas developed pathologically in human beings. In dogs 

 regeneration of the divided bile-duct may take place. 



EXCRETION OF BILE. 



This takes place : 



1. Through the constant advance of fresh amounts of bile from the 

 seat of production toward the excretory ducts. 



2. Through the periodic compression of the liver by the diaphragm 

 from above, with each inspiration. In addition, each inspiration accel- 

 erates the blood-current in the hepatic veins ; each respiratory increase in 

 abdominal pressure hastens the blood-current in the portal vein. 



Whether the diminution in the secretion of bile following bilateral division 

 of the pneumogastric nerves is to be explained in this manner has been decided 

 in the affirmative. Nevertheless it is to be borne in mind that the pneumogastric 

 nerve sends branches to the hepatic plexus. Whether the excretion of bile is 

 also decreased after paralysis of the phrenic nerves and relaxation of the abdom- 

 inal pressure is undetermined. 



3. By the peristaltic contraction, every fifteen or twenty seconds, of 

 the unstriped muscle-fibers of the large biliary ducts and the gall-bladder, 

 the secretion is forced onward. Stimulation of the region of the spinal 

 cord, from which the motor nerves for these structures are derived 

 (through the splanchnic nerves), for this reason induces acceleration 

 of the discharge, which is later followed by retardation. Under normal 

 circumstances this stimulation appears to be due to reflex action, ex- 

 cited by the entrance of the ingesta into the duodenum, in conjunc- 

 tion with stimulation of the movement of this portion of the intestine. 



The movement of the biliary ducts can be in part excited, in part inhibited 

 reflexly by stimulation of the central end of the pneumogastric or of the sciatic 

 nerve. According to Oddi, the common bile-duct is provided with a sphincter 

 at its duodenal orifice, which is affected by reflex influences: gastro-intestinal 

 irritation is believed to cause spastic contraction, which would not be unimportant 

 in the explanation of attacks of jaundice of nervous origin. 



4. Direct stimulation of the liver or reflex stimulation of the spinal 

 cord retards the excretion. On the other hand, extirpation of the hepatic 

 plexus, as well as injury to the floor of the fourth ventricle, has no dis- 

 turbing influence. The splanchnic nerve is the motor nerve of the bile- 

 ducts and the gall-bladder. Stimulation of its central extremity causes 

 relaxation of ducts and bladder, while stimulation of the central end of 

 the pneumogastric nerve causes their contraction, together with relaxa- 

 tion of the sphincter of the duodenal orifice. 



